1. Field of the Invention
The present invention relates to an optical module utilized in an optical transceiver and the like for linking and unlinking.
2. Related Background Art
In high-speed LANs (Local Area Networks), optical transceivers have widely been in use as a module for converting digital electric signals and optical signals to each other. In order to attain a higher density in ports of hub apparatus and the like using such optical transceivers, SFF (Small Form Factor) has been known as a unified standard enabling a smaller size. While such SFF optical transceivers are characterized by their small size and low power consumption, SFP (Small Form Factor Pluggable) optical transceivers making electric connectors attachable thereto and detachable therefrom without stopping devices have further been developed.
As LANs attain a higher speed, digital signals transmitted by such an SFF or SFP optical transceiver have been shifting to a gigabit band. In the SFF or SFP optical transceiver, due to its small size, its optical transmitter unit and optical receiver unit are located close to each other, whereby they are likely to interfere with each other when dealing with digital signals having such a high frequency. Also, they are susceptible to external noise, whereby the sensitivity of such an optical transceiver is more likely to be deteriorated by crosstalk as compared with optical transceivers having a large size.
Therefore, it is an object of the present invention to provide an optical module used in an optical transceiver or the like, which suppresses the interference between its optical transmitter unit and optical receiver unit, and the influence of noise, thereby improving characteristics.
For overcoming the above-mentioned problem, the present invention provides an optical module comprising, within a housing, a substrate having an electronic circuit, and light-emitting and light-receiving device units each having an optical output or input end connected to the electronic circuit; (1) wherein a connecting part of the electronic circuit to the light-emitting device unit comprises respective signal lines for normal and opposite phases arranged on both sides of a light-emitting device reference voltage line disposed at a center, and respective reference voltage lines disposed on outer sides of the signal lines, the signal lines and reference voltage lines being electrically connected to respective lead pins extending from the light-emitting device unit, and a conductive light-emitting device bracket which surrounds the lead pins extending from the light-emitting device unit and is electrically connected to the reference voltage lines on both ends of the electronic circuit; or (2) wherein a connecting part of the electronic circuit to the light-receiving device unit comprises respective reference voltage lines arranged on both sides of a signal line, the signal line and reference voltage lines being electrically connected to respective lead pins extending from the light-receiving device unit, and a conductive light-receiving device bracket which surrounds the lead pins extending from the light-receiving device unit and is electrically connected to the reference voltage lines on both ends of the electronic circuit.
When the lead pins extending from the light-emitting device unit and/or light-receiving device unit are electrically shielded with a light-emitting device bracket and/or light-receiving device bracket as such while signal lines are held between reference voltage lines, potentials are stabilized, and mutual interference and influences of external noise can be suppressed. As a consequence, characteristics improve.
Preferably, the light-emitting device bracket or light-receiving device bracket is electrically connected to a metal part of an enclosure of its corresponding light-emitting device unit or light-receiving device unit. This can stabilize reference voltages of the light-emitting device and light-receiving device, whereby stable characteristics can be obtained.